What is dynamic surface tension measurement

Surface tension is a proprietary term with a clear definition, while dynamic surface tension is a non proprietary term without a clear definition. Various industries have different understandings and demands for dynamic surface tension, some of which are changes in surface tension over time, some are changes in surface tension with bubble pressure, some are changes in surface tension with concentration, and so on. For example, the petroleum industry mostly adopts the second option, occasionally using the first option:

1. Dynamic surface tension can be understood as the surface tension that changes over time, for example, the horizontal axis of the measurement curve for measuring surface tension using platinum plate method or platinum ring method is time.

2. Dynamic surface tension can be understood as the interfacial tension between liquid air or liquid under high-speed rotation from 6000 rpm to 10000 rpm, such as measuring ultra-low interfacial tension using the spin drop method.

3. Dynamic surface tension can be understood as the process of slowly extruding liquid from a flat needle, forming droplets, and then dropping them, where the surface tension is measured by the hanging drop method.

4. Dynamic surface tension can be understood as the change in liquid surface tension, measured by the bubble pressure method, as the speed of bubble formation accelerates from 1 bubble/second to 20 bubbles/second in a liquid. The horizontal axis of the curve represents the number of bubbles formed per second.

5. Dynamic surface tension can be understood as the varying time required for different surfactants to migrate to a new interface. During the migration process of surfactants, surface tension is constantly changing. For example, the print head of an inkjet printer only takes a few tens of milliseconds (or less) to print onto paper, while spraying car paint onto a workpiece or rolling latex paint onto a wall may take tens to thousands of milliseconds.

6. Dynamic surface tension can be understood as automatically measuring the surface tension of a series of surfactant solutions with different concentrations, while recording the γ - c (concentration) curve. By fitting the curve, the inflection point can be automatically identified and the critical micelle concentration CMC of the surfactant in this system can be calculated. Plot the logarithm of surface tension and concentration. When the surface adsorption reaches saturation, the curve shows a turning point, and the concentration at this point is CMC. The surface tension of a surfactant aqueous solution initially decreases sharply with increasing solution concentration, and then changes slowly or no longer after reaching a certain concentration (i.e. CMC). Therefore, the logarithmic plot of surface tension concentration is commonly used to determine CMC. The critical micelle concentration is the lowest concentration at which surfactant molecules combine to form micelles in a solvent, and the horizontal axis of the curve represents the concentration.